Let's say that you have a primary buyer account, that already have a some balance in the pocket, and you want to share those balance into another buyer account under your company.
You can simply open Buyer > Account > Edit (chose the buyer that you want to get the balance) > Chose "Use Balance" and select the buyer account that will share the amount.
Note that you cannot have a notification when the buyer balance reach certain of amount when the buyer account not using their own balance. To further detail about this feature you may read our knowledge based as below :
How to have a notification when the buyer balance reach certain of amount ?